Astrobiology and the Search for Life Beyond Earth in the Next Decade

Statement of

Dr. Andrew SiemionBerkeley SETI Research Center, University of California, Berkeley

ASTRON − Netherlands Institute for Radio Astronomy, Dwingeloo, NetherlandsRadboud University, Nijmegen, Netherlands

to the

Committee on Science, Space and TechnologyUnited States House of Representatives

114th United States Congress

September 29, 2015

Chairman Smith, Ranking Member Johnson and Members of the Committee, thank youfor the opportunity to testify today.

Overview

Nearly 14 billion years ago, our universe was born from a swirling quantum soup, in aspectacular and dynamic event known as the “big bang.” After several hundred million years,the first stars lit up the cosmos, and many hundreds of millions of years later, the remnantsof countless stellar explosions coalesced into the first planetary systems. Somehow, througha process still not understood, the laws of physics guiding the unfolding of our universe gaverise to self-replicating organisms − life. Yet more perplexing, this life eventually evolved acapacity to know its universe, to study it, and to question its own existence. Did this happenmany times? If it did, how? If it didn’t, why?

SETI (Search for ExtraTerrestrial Intelligence) experiments seek to determine the dis-tribution of advanced life in the universe through detecting the presence of technology,usually by searching for electromagnetic emission from communication technology, but alsoby searching for evidence of large scale energy usage or interstellar propulsion. Technologyis thus used as a proxy for intelligence − if an advanced technology exists, so to does the ad-vanced life that created it. Although natural astrophysical sources produce a diverse array ofelectromagnetic, gravitational and high energy particle emission, there are particular typesof emission that, as far as we know, could only be generated by an advanced technology.For example, technology constructed by human beings has been producing radio emissionfor more than 100 years that would be readily detectable at dozens of light years using re-ceiving technology only moderately more advanced than our own. Some emission, includingthat produced by the planetary radars at Arecibo Observatory and the NASA Deep SpaceNetwork, would be detectable across our galaxy.

Technologies far more advanced than our own could potentially produce even more dra-matic evidence of their presence. Large stellar-scale structures could cause apparent modu-lation in starlight as they orbited their host, and massive energy usage by a super advancedcivilization might be revealed by its thermodynamic signature, even from millions of light-years away.

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Although we know of only one example of life anywhere in the universe, we have reasonsto be optimistic about the possibility of life beyond Earth. Earth-like planets, water andcomplex chemistry have now been found in abundance throughout our galaxy. Everythingthat we believe was necessary for life to begin on Earth is now known to be ubiquitousthroughout our galaxy and beyond. Knowing that extraterrestrial life could exist, the race ison to discover whether or not it, in fact, does exist. Yet more compelling is the possibility thatextraterrestrial life may have followed a similar developmental process as life on the Earth,and given rise to a life form possessing intelligence and a technological capability similar to,or perhaps far exceeding, our own. Conducting direct searches for advanced extraterrestriallife is the sole means of determining the prevalence of such life in the universe, and answeringone of our most fundamental questions: Are we alone?

Radio and Optical SETI

The motivation for radio searches for extraterrestrial intelligence can be summarized asfollows: 1. coherent radio emission is commonly produced by advanced technology (judgingby Earth’s technological development), 2. electromagnetic radiation can convey informationat the maximum velocity currently known to be possible, 3. radio photons are energeticallycheap to produce, 4. certain types of coherent radio emissions are easily distinguished fromastrophysical background sources, 5. these emissions can transit vast regions of interstellarspace relatively unaffected by gas, plasma and dust. These arguments are unaffected byvarying assumptions about the motivation of the transmitting intelligence, e.g. whether thesignal transmitted is intentional or unintentional, and can be applied roughly equally to avariety of potential signal types or modulation schemes. Modern radio SETI experimentshave been ongoing for the last 55 years, but for the most part they have searched only asmall fraction of the radio spectrum accessible from the surface of the Earth and have probedonly a few nearby stars at high sensitivity.

Large national radio telescopes in the United States, such as the Green Bank Telescopein West Virginia and the Arecibo Observatory in Puerto Rico are superb facilities for a widerange of astronomy, including pulsar studies that could lead to the detection of low-frequencygravitational radiation, mapping the atomic and molecular content of nearby galaxies, andprobing the earliest epochs of the universe. In addition, these facilities are among the world’sbest at searching for the faint whispers of distant technologies. Figure 1 illustrates the naturallow noise portion of the radio spectrum between 1−10 GHz, and the approximate locations inthe radio spectrum where several different types of terrestrial transmitters produce emission.The Green Bank Telescope and Arecibo Observatory can conduct observations across thisentire range of the radio spectrum.

Earlier this year, a group of astronomy, engineering and physics students and staff fromour team at UC Berkeley, working with our colleagues from the National Radio AstronomyObservatory, installed a new instrument at the Green Bank Telescope that enables us to con-duct SETI observations in parallel with other astronomers, a technique we call “piggy-back”observing. This project was funded by a combination of support from the NASA Astrobi-ology Program, the National Science Foundation and the John Templeton Foundation, butNASA no longer provides funding for SETI experiments.

In addition to the Green Bank Telescope, other radio SETI programs are underway inthe United States at Arecibo Observatory and the private Allen Telescope Array in Northern

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Figure 1: The centimeter-wavelength portion of the electromagnetic spectrum, showing the natural rela-tively low-noise region between 1-10 GHz. At low frequencies, background radiation from our own galaxyproduces significant noise. Above 15 GHz, the oxygen and water in the Earth’s atmosphere both attenuatesincoming radiation and produces noise. Also indicated in the figure are the approximate locations in theradio spectrum where terrestrial transmitters produce emission.

California. Many international radio telescopes are also currently being used for radio SETIsearches, including the Low Frequency Array (LOFAR) in Europe, the Murchison WidefieldArray (MWA) in Australia and the Lovell Telescope at Jodrell Bank Observatory in theUnited Kingdom.

While the dominant paradigm in SETI research involves searching the radio portionof the electromagnetic spectrum, other wavelengths possess merit as well. Similar to ourconsideration of radio emission from human technology as an example of a potentially de-tectable signal from extraterrestrial intelligences, we can conceive of ways in which humantechnologies operating at other wavelengths could produce signatures detectable at interstel-lar distances. For example, laser technology already developed on Earth could be used toproduce a signal that could outshine the sun by many orders of magnitude at a distance ofmore than 1000 lightyears.

These optical and infrared SETI experiments come in two varieties, searches for pulses

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of light of short duration and searches for light emission at a single wavelength using a spec-trometer. Relative to radio transmissions, optical signals could potentially convey much moreinformation content and are more easily focused for directed signaling or communication.

At one of the world’s premier optical telescopes, the Keck Observatory on Mauna Kea,Hawaii (Figure 2), students and faculty at UC Berkeley are pursuing a search for continuousartificial lasers, using optical spectra that are collected for the primary purpose of searchingfor and characterizing extrasolar planets. In an additional effort, a group led by studentsand faculty at UC San Diego are using the Lick Observatory, near San Jose, California, toconduct a search for pulsed lasers in the near-infrared part of the electromagnetic spectrum(Figure 3), wavelengths just a hair longer than optical light − the first SETI experimentever to operate at this wavelength. Other optical SETI experiments are currently operatingor under development at Harvard University and several research institutes in France andItaly.

Ensuring that facilities like the Green Bank Telescope, Arecibo and Keck Observatorycontinue to exist as world class astronomical observatories is critical to their continued avail-ability for SETI experiments.

Figure 2: Optical SETI, searches for laser emission from advanced civilizations, are conducted at the KeckObservatory on Mauna Kea, Hawaii.

Data Mining SETI

The era of the “virtual observatory” has arrived. Many astronomers no longer need to travelthousands of miles to a telescope and command an instrument to perform observations.

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Figure 3: Near-Infrared “Optical” SETI at Lick Observatory. Professor Shelley Wright from UC SanDiego (left) leads a team that includes Professor Frank Drake (middle) and Remington Stone (right) usingthe “Nickel” telescope to search for short pulses of near-infrared light that might originate from an advancedtechnology.

Hundreds of terabytes of astronomical data, collected with billion dollar telescopes, are nowfreely available. In many cases, these data are made available to the entire astronomicalcommunity the instant they are collected. These data undoubtedly contain many astronom-ical discoveries that are as yet uncovered. Perhaps, if looked at very closely in a novel way,some of these data contain evidence of an extraterrestrial intelligence.

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The astronomical literature is rife with speculation that very advanced intelligences mayproduce signatures detectable by traditional astronomical observations. Massive “Dyson”structures, so named after they were first proposed by physicist Freeman Dyson, might bebe built to harvest the energy of hundreds of Suns and could be detected in the latestgeneration of infrared sky surveys. Figure 4 shows three hypothetical configurations of theseDyson structures orbiting a parent star. A very advanced civilization using a naturallybright astronomical source as a pseudo-artificial beacon, such as modulation of a naturallyexpanding and contracting star or interference with a pulsar, could be discovered throughcareful analysis of variable star or pulsar observations.

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Figure 4: Three hypothetical Dyson structures, a ring (left), and more numerous configurations (middleand right). Such a collection of solar collectors could allow a very advanced civilization to harvest a largefraction of the energy from their star.

Researchers at Penn State University, led by Prof. Jason Wright, have recently under-taken a significant effort to search for evidence of massive energy usage by very advancedcivilizations using data from NASA’s WISE space telescope. Although so far this work hasproduced only negative results, it has placed significant constraints on the presence of ex-tremely advanced galactic-scale civilizations. Additional work led by Dr. Erik Zackrissonin Sweden and Prof. Michael Garrett in the Netherlands has come to similar conclusionsregarding the rarity of super-advanced civilizations, but this collected work represents apromising and growing new area of SETI research.

“Open science” and “open data” policies are incredibly important for enabling innovativeSETI research using archive data from national facilities.

The Next Ten Years

It is undoubtable that the next decade will be an incredibly exciting time for astrobiology.Data provided by missions like the Transiting Exoplanet Survey Satellite (TESS) and theJames Webb Space Telescope (JWST) virtually guarantee dramatic new insights into exo-planet science, including identifying and characterizing some of the nearest exoplanets to theEarth. At the same time, we will continue to learn more about the development of life onEarth and the potential for life elsewhere in our own Solar System. If history is any guide,these discoveries will only heighten our imagination about the possibilities for advanced life

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elsewhere in the Universe. Two of the most exciting prospects for advances in SETI researchare described below.

The Breakthrough Prize Foundation1 has recently announced the Breakthrough Listenand Message Initiatives2 − two programs that will investigate the possibility of life beyondEarth and the relationship between humanity and life in the universe. Breakthrough Listen isa $100M 10−year effort to conduct the most sensitive, comprehensive and intensive search foradvanced intelligent life on other worlds ever performed. Figure 5 shows the three facilitiesthat will be employed in the Breakthrough Listen Initiative, the Green Bank Telescope (GBT)in West Virginia (Figure 5a), the Parkes Telescope in New South Wales, Australia (Figure 5b)and the Automated Planet Finder (APF) at Lick Observatory, Mount Hamilton, California(Figure 5c).

Using the GBT and Parkes, Breakthrough Listen will conduct deep observations of1,000,000 of the nearest stars to the Earth that will be at least 10 times more sensitivethan ever performed and will cover at least 5 times more of the radio spectrum. Break-through Listen will also conduct an unprecedented complete survey of the entire plane of theMilky Way Galaxy, as well as surveys of more than 100 other galaxies, including all galax-ies in the Milky Way’s Local Group. The sensitivity of the Green Bank, expressed as theluminosity (power) detectable as a function of the transmitter distance, is shown in Figure6. As shown, the Green Bank Telescope could detect an extraterrestrial radio transmitterwith the same luminosity as our own most powerful radar (the Arecibo Planetary Radar),in 1 minute each, for more than 1 million nearby stars.

Using a robotic optical telescope at Lick Observatory, the APF with its “Levy Spec-trometer,” Breakthrough Listen will observe 1000 nearby stars and 100 galaxies searchingfor artificial laser emission. These observations will be performed over wavelengths from374−950 nm, including the near ultraviolet, the entire visible, and near infrared portion ofthe electromagnetic spectrum. Breakthrough Listen will detect lasers with any power above100 Watts from the nearest stars and above 1000 Gigawatts from the nearest galaxies.

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Figure 5: The three facilities to be used in the Breakthrough Listen Initiative. From left to right, (a) TheGreen Bank Telescope, Green Bank, West Virginia (b) The Parkes Telescope, New South Wales, Australia(c) The Automated Planet Finder, Lick Observatory, Mount Hamilton, California

The Square Kilometre Array (SKA) project is an international partnership that seeks toconstruct the world’s largest radio telescope operating at meter and centimeter wavelengths,

1http://breakthroughprize.org2http://breakthroughinitiatives.org

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Figure 6: The sensitivity of the Green Bank Telescope expressed as the luminosity detectable as a functionof the transmitter distance. Both 1 minute and 24 hour observation durations are indicated. The detectableluminosity is indicated in units of the luminosity of the Arecibo Planetary Radar − the most powerful radiotransmitter on Earth. As shown, the Green Bank Telescope could detect a radio transmitter with the sameluminosity as the Arecibo Planetary Radar, in 1 minute each, for more than 1 million nearby stars.

eventually achieving a full square kilometer (1 km2) of collecting area for some components.Such a telescope, as envisioned, would be the most powerful radio telescope in the world,surpassing all current facilities by an order of magnitude or more in sheer sensitivity. PhaseI of the SKA is expected to be built in Southern Africa and Southern Australia, with themid-frequency (centimeter-wave, SKA1-MID) and low frequency (SKA1-LOW, meter-wave)components split between the two sites respectively. The SKA Headquarters is located at theJodrell Bank Observatory near Manchester, UK. There are 10 SKA member countries, andapproximately 100 organizations from 20 countries participating in its development. TheUnited States is not currently an SKA member country.

The SKA will offer revolutionary new observational capabilities for SETI, allowing sen-sitive targeted SETI observations to be performed alongside other astronomical research.Rather than simply “piggy-backing,” SETI observers will be able to independently pointthe telescope at targets of interest using high speed digital beamforming. SKA construc-tion is expected to be completed in two phases. SKA Phase 1 will include a low frequency(SKA1-LOW, 50 350 MHz) array component made up of 130,000 dipole antennas sited inSouthern Australia (Figure 7a) and a 200-dish mid-frequency (SKA1-MID, 350 14000 MHz)component sited in Southern Africa (Figure 7b). SKA Phase 2 will complete telescope con-struction at both sites and could include augmentation with new mid-frequency aperturearray technology that could dramatically expand the telescopes primary field of view.

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SKA may be the first telescope capable of detecting truly Earth−like leakage radiationfrom nearby stars, allowing us our best chance at detecting another civilization with anartificial radio signature similar to our own.

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Figure 7: Artist impressions of the two components of the first phase of the Square Kilometre Array (SKA):SKA1-LOW (left) is a low frequency facility operating from 50−350 MHz sited in Southern Australia. SKA1-MID, operating from 350−14000 MHz will be built in South Africa.

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Dr. Andrew P. V. Siemion

Short Narrative Biography

Dr. Andrew Siemion is an astrophysicist at the University of California (UC), Berkeleyand serves as Director of the UC Berkeley Center for Search for Extraterrestrial Intelligence(SETI) Research. He is jointly affiliated with The Netherlands Institute for Radio Astron-omy (ASTRON) and Radboud University, Nijmegen, Netherlands. Dr. Siemion’s researchinterests include studies of time-variable celestial phenomena, astronomical instrumentationand SETI. Dr. Siemion is one of the leaders of the “Breakthrough Listen Initiative” − a10 year, 100 million dollar effort, sponsored by Yuri Milner’s Breakthrough Prize Founda-tion, that is conducting the most sensitive, comprehensive and intensive search for advancedextraterrestrial life in history.

Dr. Siemion was a recipient of the Josephine De Karman Fellowship for UndergraduateStudies at UC Berkeley, the UC Berkeley Dorothea Klumpke Roberts Prize for outstandingscholarship as an undergraduate major in astrophysics and the UC Berkeley Mary ElizabethUhl PhD Dissertation Prize for his work on searches for exotic radio phenomena. Dr. Siemionis an elected member of the International Union of Radio Science, in which he serves as anEarly Career Representative for the Commission on Radio Astronomy, and the InternationalAcademy of Astronautics’ SETI Permanent Committee, in which he serves as CommitteeSecretary. Dr. Siemion also serves on the Science@Cal Advisory Board, Co-Chairs theCradle of Life Science Working Group for the forthcoming Square Kilometer Array telescopeand is a member of the Board of Directors of the Foundation for Investing in Research onSETI Science and Technology (FIRSST).

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